Total dimensional stability compensation system and method for magnetic tape drive

ABSTRACT

A tape drive includes a first tape head, a first actuator assembly, a second tape head, a second actuator assembly, and a controller. The first tape head includes two first servo elements that each read one of two servo tracks, and a first read/write element that one of reads data from and writes data to a first data track. The first tape head is positionable at a first base head rotation angle. The first actuator assembly selectively rotates the first tape head from the first base head rotation angle to a first adjusted head rotation angle. The second tape head includes two second servo elements that each read one of the two servo tracks, and a second read/write element that one of reads data from and writes data to the first data track. The second tape head is positionable at a second base head rotation angle. The second actuator assembly selectively rotates the second tape head from the second base head rotation angle to a second adjusted head rotation angle. The controller independently controls the selective rotation of the first tape head and the second tape head based solely on servo information.

The present invention is directed toward a tape drive for use with a magnetic tape including two spaced apart servo tracks and a first data track that is positioned substantially between the two servo tracks along a length of the magnetic tape. In various embodiments, the tape drive includes a first tape head, a first actuator assembly, a second tape head, a second actuator assembly, and a controller. The first tape head includes two spaced apart first servo elements that are each configured to read one of the two servo tracks, and a first read/write element that is configured to one of read data from the first data track and write data to the first data track. The first tape head is positionable at a first base head rotation angle relative to transverse to the length of the magnetic tape. The first actuator assembly is configured to selectively rotate the first tape head relative to the magnetic tape from the first base head rotation angle to a first adjusted head rotation angle that is different than the first base head rotation angle. The second tape head includes two spaced apart second servo elements that are each configured to read one of the two servo tracks, and a second read/write element that is configured to one of read data from the first data track and write data to the first data track. The second tape head is positionable at a second base head rotation angle relative to transverse to the length of the magnetic tape. The second actuator assembly is configured to selectively rotate the second tape head relative to the magnetic tape from the second base head rotation angle to a second adjusted head rotation angle that is different than the second base head rotation angle. The controller (i) controls the first actuator assembly to selectively rotate the first tape head relative to the magnetic tape from the first base head rotation angle to the first adjusted head rotation angle based solely on servo information from the two first servo elements reading the two servo tracks; and (ii) controls the second actuator assembly to selectively rotate the second tape head relative to the magnetic tape from the second base head rotation angle to the second adjusted head rotation angle based solely on servo information from the two second servo elements reading the two servo tracks, the controller controlling the second actuator assembly independently of the first actuator assembly.

In some embodiments, the controller (i) controls the first actuator assembly to selectively rotate the first tape head relative to the magnetic tape from the first base head rotation angle to the first adjusted head rotation angle based solely on timing-based servo information from the two first servo elements reading the two servo tracks; and (ii) controls the second actuator assembly to selectively rotate the second tape head relative to the magnetic tape from the second base head rotation angle to the second adjusted head rotation angle based solely on timing-based servo information from the two second servo elements reading the two servo tracks.

In certain embodiments, the magnetic tape includes a plurality of data tracks that are positioned substantially between the two spaced apart servo tracks along the length of the magnetic tape; the first tape head includes a plurality of read/write elements that are each configured to one of read data from one of the plurality of data tracks and write data to one of the plurality of data tracks; and the second tape head includes a plurality of read/write elements that are each configured to one of read data from one of the plurality of data tracks and write data to one of the plurality of data tracks.

In some embodiments, at least one of the first base head rotation angle and the second base head rotation angle is between approximately one degree and 45 degrees relative to transverse to the length of the magnetic tape.

In certain embodiments, at least one of the first adjusted head rotation angle and the second adjusted head rotation angle is between approximately zero degrees and 60 degrees relative to transverse to the length of the magnetic tape.

In some embodiments, at least one of the first base head rotation angle and the second base head rotation angle is between approximately five degrees and 15 degrees relative to transverse to the length of the magnetic tape.

In certain embodiments, at least one of the first adjusted head rotation angle and the second adjusted head rotation angle is between approximately zero degrees and 25 degrees relative to transverse to the length of the magnetic tape.

In many embodiments, the two spaced apart servo tracks are spaced apart by a servo track spacing. In some embodiments, the first base head rotation angle is controlled by the controller so that each of the two spaced apart first servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by the servo track spacing; and the second base head rotation angle is controlled by the controller so that each of the two spaced apart second servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by the servo track spacing.

In certain embodiments, changes in environmental conditions cause a change in the servo track spacing to an adjusted servo track spacing. In some embodiments, the first adjusted head rotation angle is controlled by the controller so that each of the two spaced apart first servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by the adjusted servo track spacing; and the second adjusted head rotation angle is controlled by the controller so that each of the two spaced apart second servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by the adjusted servo track spacing.

In certain embodiments, the first tape head includes a center of mass; and the first actuator assembly is configured to rotate the first tape head relative to the magnetic tape about a first pivot point that is positioned at the center of mass of the first tape head.

In some embodiments, the second tape head includes a center of mass; and the second actuator assembly is configured to rotate the second tape head relative to the magnetic tape about a second pivot point that is positioned at the center of mass of the second tape head.

In many embodiments, the first actuator assembly is further configured to move the first tape head transversely relative to the magnetic tape; and the second actuator assembly is further configured to move the second tape head transversely relative to the magnetic tape.

The present invention is also directed toward a tape drive for use with a magnetic tape including two spaced apart servo tracks and a first data track that are positioned along a length of the magnetic tape, the tape drive including (A) a tape head assembly including (i) at least two servo elements that are each configured to read one of the two servo tracks, (ii) a first read/write element that is configured to one of read data from the first data track and write data to the first data track, the first read/write element being positionable at a first base rotation angle relative to transverse to the length of the magnetic tape, and (iii) a second read/write element that is configured to one of read data from the first data track and write data to the first data track, the second read/write element being positionable at a second base rotation angle relative to transverse to the length of the magnetic tape; (B) an actuator assembly that is configured to (i) selectively rotate the first read/write element relative to the magnetic tape from the first base rotation angle to a first adjusted rotation angle that is different than the first base rotation angle, and (ii) selectively rotate the second read/write element relative to the magnetic tape from the second base rotation angle to a second adjusted rotation angle that is different than the second base rotation angle; and (C) a controller that controls the actuator assembly to selectively and independently (i) rotate the first read/write element relative to the magnetic tape from the first base rotation angle to the first adjusted rotation angle based solely on servo information from the at least two servo elements reading the two servo tracks, and (ii) rotate the second read/write element relative to the magnetic tape from the second base rotation angle to the second adjusted rotation angle based solely on servo information from the at least two servo elements reading the two servo tracks.

The present invention is further directed toward a tape drive for use with a magnetic tape including two spaced apart servo tracks that are spaced apart by a servo track spacing and a plurality of data tracks that are positioned substantially between the two servo tracks along a length of the magnetic tape, the tape drive including (A) a first tape head including two spaced apart first servo elements that are each configured to read one of the two servo tracks, and a plurality of first read/write elements that are each configured to one of read data from one of the plurality of data tracks and write data to one of the plurality of data tracks, the first tape head being positionable at a first base head rotation angle of between approximately one degree and 45 degrees relative to transverse to the length of the magnetic tape; (B) a first actuator assembly that is configured to selectively rotate the first tape head relative to the magnetic tape from the first base head rotation angle to a first adjusted head rotation angle that is different than the first base head rotation angle, the first adjusted head rotation angle being between approximately zero degrees and 60 degrees relative to transverse to the length of the magnetic tape; (C) a second tape head including two spaced apart second servo elements that are each configured to read one of the two servo tracks, and a plurality of second read/write elements that are each configured to one of read data from one of the plurality of data tracks and write data to one of the plurality of data tracks, the second tape head being positionable at a second base head rotation angle of between approximately one degree and 45 degrees relative to transverse to the length of the magnetic tape; (D) a second actuator assembly that is configured to selectively rotate the second tape head relative to the magnetic tape from the second base head rotation angle to a second adjusted head rotation angle that is different than the second base head rotation angle, the second adjusted head rotation angle being between approximately zero degrees and 60 degrees relative to transverse to the length of the magnetic tape; and (E) a controller that selectively and independently (i) controls the first actuator assembly to selectively rotate the first tape head relative to the magnetic tape from the first base head rotation angle to the first adjusted head rotation angle based solely on servo information from the two first servo elements reading the two servo tracks; and (ii) controls the second actuator assembly to selectively rotate the second tape head relative to the magnetic tape from the second base head rotation angle to the second adjusted head rotation angle based solely on servo information from the two second servo elements reading the two servo tracks; wherein the first base head rotation angle is controlled by the controller so that each of the two spaced apart first servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by the servo track spacing; wherein the second base head rotation angle is controlled by the controller so that each of the two spaced apart second servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by the servo track spacing; wherein changes in environment conditions cause a change in the servo track spacing to an adjusted servo track spacing; wherein the first adjusted head rotation angle is controlled by the controller so that each of the two spaced apart first servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by the adjusted servo track spacing; and wherein the second adjusted head rotation angle is controlled by the controller so that each of the two spaced apart second servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by 

1. A tape drive for use with a magnetic tape including two spaced apart servo tracks and a first data track that is positioned substantially between the two servo tracks along a length of the magnetic tape, the tape drive comprising: a first tape head including two spaced apart first servo elements that are each configured to read one of the two servo tracks, and a first read/write element that is configured to one of read data from the first data track and write data to the first data track, the first tape head being positionable at a first base head rotation angle relative to transverse to the length of the magnetic tape; a first actuator assembly that is configured to selectively rotate the first tape head relative to the magnetic tape from the first base head rotation angle to a first adjusted head rotation angle that is different than the first base head rotation angle; a second tape head including two spaced apart second servo elements that are each configured to read one of the two servo tracks, and a second read/write element that is configured to one of read data from the first data track and write data to the first data track, the second tape head being positionable at a second base head rotation angle relative to transverse to the length of the magnetic tape; a second actuator assembly that is configured to selectively rotate the second tape head relative to the magnetic tape from the second base head rotation angle to a second adjusted head rotation angle that is different than the second base head rotation angle; and a controller that (i) controls the first actuator assembly to selectively rotate the first tape head relative to the magnetic tape from the first base head rotation angle to the first adjusted head rotation angle based solely on servo information from the two first servo elements reading the two servo tracks; and (ii) controls the second actuator assembly to selectively rotate the second tape head relative to the magnetic tape from the second base head rotation angle to the second adjusted head rotation angle based solely on servo information from the two second servo elements reading the two servo tracks, the controller controlling the second actuator assembly independently of the first actuator assembly.
 2. The tape drive of claim 1 wherein the controller (i) controls the first actuator assembly to selectively rotate the first tape head relative to the magnetic tape from the first base head rotation angle to the first adjusted head rotation angle based solely on timing-based servo information from the two first servo elements reading the two servo tracks; and (ii) controls the second actuator assembly to selectively rotate the second tape head relative to the magnetic tape from the second base head rotation angle to the second adjusted head rotation angle based solely on timing-based servo information from the two second servo elements reading the two servo tracks.
 3. The tape drive of claim 1 wherein the magnetic tape includes a plurality of data tracks that are positioned substantially between the two spaced apart servo tracks along the length of the magnetic tape; wherein the first tape head includes a plurality of read/write elements that are each configured to one of read data from one of the plurality of data tracks and write data to one of the plurality of data tracks; and wherein the second tape head includes a plurality of read/write elements that are each configured to one of read data from one of the plurality of data tracks and write data to one of the plurality of data tracks.
 4. The tape drive of claim 1 wherein at least one of the first base head rotation angle and the second base head rotation angle is between approximately one degree and 45 degrees relative to transverse to the length of the magnetic tape.
 5. The tape drive of claim 4 wherein at least one of the first adjusted head rotation angle and the second adjusted head rotation angle is between approximately zero degrees and 60 degrees relative to transverse to the length of the magnetic tape.
 6. The tape drive of claim 1 wherein at least one of the first base head rotation angle and the second base head rotation angle is between approximately five degrees and 15 degrees relative to transverse to the length of the magnetic tape.
 7. The tape drive of claim 6 wherein at least one of the first adjusted head rotation angle and the second adjusted head rotation angle is between approximately zero degrees and 25 degrees relative to transverse to the length of the magnetic tape.
 8. The tape drive of claim 1 wherein the two spaced apart servo tracks are spaced apart by a servo track spacing; wherein the first base head rotation angle is controlled by the controller so that each of the two spaced apart first servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by the servo track spacing; and wherein the second base head rotation angle is controlled by the controller so that each of the two spaced apart second servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by the servo track spacing.
 9. The tape drive of claim 8 wherein changes in environmental conditions cause a change in the servo track spacing to an adjusted servo track spacing; wherein the first adjusted head rotation angle is controlled by the controller so that each of the two spaced apart first servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by the adjusted servo track spacing; and wherein the second adjusted head rotation angle is controlled by the controller so that each of the two spaced apart second servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by the adjusted servo track spacing.
 10. The tape drive of claim 1 wherein the first tape head includes a center of mass; and wherein the first actuator assembly is configured to rotate the first tape head relative to the magnetic tape about a first pivot point that is positioned at the center of mass of the first tape head.
 11. The tape drive of claim 10 wherein the second tape head includes a center of mass; and wherein the second actuator assembly is configured to rotate the second tape head relative to the magnetic tape about a second pivot point that is positioned at the center of mass of the second tape head.
 12. The tape drive of claim 1 wherein the first actuator assembly is further configured to move the first tape head transversely relative to the magnetic tape; and wherein the second actuator assembly is further configured to move the second tape head transversely relative to the magnetic tape.
 13. A tape drive for use with a magnetic tape including two spaced apart servo tracks and a first data track that are positioned along a length of the magnetic tape, the tape drive comprising: a tape head assembly including (i) at least two servo elements that are each configured to read one of the two servo tracks, (ii) a first read/write element that is configured to one of read data from the first data track and write data to the first data track, the first read/write element being positionable at a first base rotation angle relative to transverse to the length of the magnetic tape, and (iii) a second read/write element that is configured to one of read data from the first data track and write data to the first data track, the second read/write element being positionable at a second base rotation angle relative to transverse to the length of the magnetic tape; an actuator assembly that is configured to (i) selectively rotate the first read/write element relative to the magnetic tape from the first base rotation angle to a first adjusted rotation angle that is different than the first base rotation angle, and (ii) selectively rotate the second read/write element relative to the magnetic tape from the second base rotation angle to a second adjusted rotation angle that is different than the second base rotation angle; and a controller that controls the actuator assembly to selectively and independently (i) rotate the first read/write element relative to the magnetic tape from the first base rotation angle to the first adjusted rotation angle based solely on servo information from the at least two servo elements reading the two servo tracks, and (ii) rotate the second read/write element relative to the magnetic tape from the second base rotation angle to the second adjusted rotation angle based solely on servo information from the at least two servo elements reading the two servo tracks.
 14. The tape drive of claim 13 wherein the controller controls the actuator assembly to selectively and independently (i) rotate the first read/write element relative to the magnetic tape from the first base rotation angle to the first adjusted rotation angle based solely on timing-based servo information from the at least two servo elements reading the two servo tracks, and (ii) rotate the second read/write element relative to the magnetic tape from the second base rotation angle to the second adjusted rotation angle based solely on timing-based servo information from the at least two servo elements reading the two servo tracks.
 15. The tape drive of claim 13 wherein the tape head assembly includes (i) a first tape head including two spaced apart first servo elements that are each configured to read one of the two servo tracks, and the first read/write element that is configured to one of read data from the first data track and write data to the first data track; and (ii) a second tape head including two spaced apart second servo elements that are each configured to read one of the two servo tracks, and the second read/write element that is configured to one of read data from the first data track and write data to the first data track.
 16. The tape drive of claim 13 wherein at least one of the first base rotation angle and the second base rotation angle is between approximately one degree and 45 degrees relative to transverse to the length of the magnetic tape.
 17. The tape drive of claim 16 wherein at least one of the first adjusted rotation angle and the second adjusted rotation angle is between approximately zero degrees and 60 degrees relative to transverse to the length of the magnetic tape.
 18. The tape drive of claim 13 wherein the tape head assembly includes a center of mass; and wherein the actuator assembly is configured to rotate the tape head assembly relative to the magnetic tape about a pivot point that is positioned at the center of mass of the tape head assembly.
 19. The tape drive of claim 13 wherein the actuator assembly is further configured to move the tape head assembly transversely relative to the magnetic tape.
 20. A tape drive for use with a magnetic tape including two spaced apart servo tracks that are spaced apart by a servo track spacing and a plurality of data tracks that are positioned substantially between the two servo tracks along a length of the magnetic tape, the tape drive comprising: a first tape head including two spaced apart first servo elements that are each configured to read one of the two servo tracks, and a plurality of first read/write elements that are each configured to one of read data from one of the plurality of data tracks and write data to one of the plurality of data tracks, the first tape head being positionable at a first base head rotation angle of between approximately one degree and 45 degrees relative to transverse to the length of the magnetic tape; a first actuator assembly that is configured to selectively rotate the first tape head relative to the magnetic tape from the first base head rotation angle to a first adjusted head rotation angle that is different than the first base head rotation angle, the first adjusted head rotation angle being between approximately zero degrees and 60 degrees relative to transverse to the length of the magnetic tape; a second tape head including two spaced apart second servo elements that are each configured to read one of the two servo tracks, and a plurality of second read/write elements that are each configured to one of read data from one of the plurality of data tracks and write data to one of the plurality of data tracks, the second tape head being positionable at a second base head rotation angle of between approximately one degree and 45 degrees relative to transverse to the length of the magnetic tape; a second actuator assembly that is configured to selectively rotate the second tape head relative to the magnetic tape from the second base head rotation angle to a second adjusted head rotation angle that is different than the second base head rotation angle, the second adjusted head rotation angle being between approximately zero degrees and 60 degrees relative to transverse to the length of the magnetic tape; and a controller that selectively and independently (i) controls the first actuator assembly to selectively rotate the first tape head relative to the magnetic tape from the first base head rotation angle to the first adjusted head rotation angle based solely on servo information from the two first servo elements reading the two servo tracks; and (ii) controls the second actuator assembly to selectively rotate the second tape head relative to the magnetic tape from the second base head rotation angle to the second adjusted head rotation angle based solely on servo information from the two second servo elements reading the two servo tracks; wherein the first base head rotation angle is controlled by the controller so that each of the two spaced apart first servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by the servo track spacing; wherein the second base head rotation angle is controlled by the controller so that each of the two spaced apart second servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by the servo track spacing; wherein changes in environment conditions cause a change in the servo track spacing to an adjusted servo track spacing; wherein the first adjusted head rotation angle is controlled by the controller so that each of the two spaced apart first servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by the adjusted servo track spacing; and wherein the second adjusted head rotation angle is controlled by the controller so that each of the two spaced apart second servo elements are positioned to read one of the two spaced apart servo tracks that are spaced apart by the adjusted servo track spacing. 